Emulsified fat spreads, especially margarines, provide many benefits which make such spreads highly desirable as butter substitutes. For instance, margarines are lower in cost than butter, while providing many of the same taste characteristics of butter. Additionally, margarines can be formulated to be lower in cholesterol than buffer, which is a benefit for the many individuals concerned with high-cholesterol diets. Margarines spread more easily than butter. However, margarines which are equal to or superior to butter in all physical attributes have not been made.
In the search to obtain margarines exhibiting the positive attributes of butter, i.e. good mouth texture, thermal stability and good spreadability, many economically desirable starting materials have been tried without success. For instance, palm oils have long been of interest for use as margarines because of their relatively low costs and preferred triglyceride compositions. Unfortunately, standard margarine processing techniques often result in a post-hardening effect which makes these palm-based margarine products very hard and brittle.
Single fractionated or "topped" palm oil fats have been used to formulate margarine products which do not exhibit the post-hardening phenomenon. U.S. Pat. No. 3,189,465 to Oakley et al, issued June 15, 1965, relates to a margarine wherein at least a major portion of the fat consists of one or more lower melting fractions of a semi-soft oil, e.g. palm oil. These lower melting fractions can be obtained by a single thermal fractionation in which the higher melting fraction containing the trisaturated glycerides is removed. These margarines, although better than margarines made from palm oil alone, do not exhibit thermal stability, and more importantly, are extremely brittle and hard to spread. Other such margarines are disclosed in U.S. Pat. No. 4,055,679 to Kattenberg et al., issued Oct. 25, 1977 (plastic fat suitable for margarines containing a palm-based fat such as palm olein co-randomized with fats such as soybean oil or safflower oil), and U.S. Pat. No. 4,087,564 to Poot et al., issued May 2, 1978 (olefin fraction obtained by single thermal fractionation of co-randomized blend of palm oil and soybean oil).
Mid-palm oil fraction fats are known in the art as cocoa butter extenders or substitutes. One example is found in U.S. Pat. No. 4,205,095 to Pike et al., issued May 27, 1980. Pike et al. describe a thermal fraction method for producing a palm mid-fraction which is then hydrogenated. Another such fat is disclosed in British Patent Specification No. 827,172 to Best et al., published Feb. 3, 1960, which relates to a method for making a cocoa butter substitute by a two-step solvent fractionation of palm oil.
The above references all relate to some treatment of the palm oil, such as fractionation, blending or co-randomization, in a effort to produce an acceptable palm-oil based margarine product.
Palm-oil based margarines possess two distinct groups of triglycerides which ultimately form different crystallization patterns. It is this difference in crystallization that is believed to account for the post-hardening phenomenon. Unfortunately, established processing techniques actually serve to enhance this inherent crystallization disadvantage because formation of homogeneous crystal types and size through processing techniques is not encouraged. Thus, relatively few references address processing changes to alleviate the problem.
In standard margarine manufacture, the aqueous phase ingredients (milk or milk solids, salt, flavors, preservatives and water) are dispersed in the oil phase (melted margarine fat, emulsifiers, color and flavors), and the mixture is then sent through a scraped wall heat exchanger known as an A unit. Besides chilling the emulsified fat, the high local pressure and shearing action of the A unit induces fast nucleation and crystallization of the triglycerides during the short residence time (0.5 to 60 seconds). The chilled emulsion is then sent to a crystallizer known as a B unit. Static B units, in the form of a hollow tube or resting tube, normally provide firm stick-type margarines. Working B units, in the form of picker boxes, serve to break up large crystals, producing smaller, purer triglyceride crystals. See Haighton, "Blending, Chilling, and Tempering of Margarines and Shortenings", J. Am. Oil Chemists Soc., Vol. 53 (June, 1976), pp. 397-399; Wiedermann, "Margarine and Margarine Oil, Formulation and Control", J. Am. Oil Chemists Soc., Vol. 55 (December, 1978), pp. 823-829.
U.S. Pat Nos. 4,217,372 and 4,087,565 to Ebskamp, issued Aug. 12, 1980 and May 2, 1978, respectively, disclose methods for improving the physical structure of fats in a margarine wherein the margarines are cooled, then mechanically worked and cooled again to a temperature lower than the first cooling. See also Chikany, "Crystallization Process of Fats and Their Role in Margarine Production. Part II", Olaj, Szappan, Kozmetika, 13: 9-13 (1982). However, even these margarines exhibit some deficiency.
Surprisingly, it has been found that a margarine that does not exhibit the post-hardening problem can be made from a margarine fat that contains fractionated palm oil and/or palm stearin. The fats used in this invention are characterized by a double-peaked differential scanning calorimetry curve representing two distinctly crystallizing triglyceride groups. Fats other than palm-based fats can be used, so long as they have this characteristic differential scanning calorimetry curve.
Furthermore, these fats are processed into emulsified spreads, such as margarines, by a method that results in uniform sizes of triglyceride crystals. The method involves cooling the emulsion; then working it; followed by a second cooling and a final working.
It is an object of the present invention, therefore, to provide emulsified spreads such as margarines having desirable mouth texture and thermal stability, with good spreadability due to the avoidance of post-hardening.
Another object of the present invention is to provide margarines and emulsified spreads made from fats containing two sets of triglycerides, one crystallizing at between about 77.degree. F. (25.degree. C.) and about 50.degree. F. (10.degree. C.), and a second group crystallizing at between about 41.degree. F. (5.degree. C.) and about 14.degree. F. (-10.degree. C.). These fats have a characteristic double-peaked differential scanning calorimetry curve as represented in FIG. 1.
These and further objects will become apparent in the disclosure of the present invention described below. All percentages are by weight of total product unless indicated to the contrary.